Ultra-short wave receiving apparatus



Aug. 30, 1938. w. KRIEBEL ULTRA-SHORT WAVE REEJEIVING APPARATUS FiledOct. 28, 1937 INVENTOR.

A El? KRIEBEL ATTOI VEY.

Patented Aug. 30, 1938 UNITED STATES PATENT orncr:

ULTRA- SHORT WAVE RECEIVING APPA- RATUS ration of Germany ApplicationOctober 28, 1937, Serial No. 171,443

Germany S 3 Claims.

The present invention relates to a tube detector for receivingultra-short waves. This detector is more sensitive than a bolometer andexhibits above all a uniform response.

The inventive idea is as follows:-

The emission source or cathode of a discharge tube, e. g. of a diode, isdirectly supplied with the high-frequency receiving current so thatheating or additional heating is effected thereby.

10 As the emission of a cathode, so long as the ap plied plate voltageby far exceeds the saturation voltage, greatly depends on the heating,relatively small variations of the receiving currents may be madeperceptible in this manner. E. g. a heat- 15 ing current variation by 1%yields an emission variation of about 20%. One reason why the platevoltage must exceed saturation voltage is to prevent space chargebetween the cathode and the plate.

A relatively simple arrangement results, if a diode is used as receivingtube and one dipole half each is attached to the ends of the straightcathode.

As the filament energy consumption varies for a given resistance of thespot to be heated with the square of the current the cathode,preferably, is initially heated by a constant but adjustable, as may berequired, direct current and the received high-frequency oscillationsare used only to render an additional heating. To avoid thehigh-frequency leaking off through the heating current leads, one mayeither design the emissive spot to be very small so that it prac=tically lies only in the voltage node of the dipole,

w or tune the heating current leads by means of a metal slider which isinsulated from the heating current leads and is sliding on them.Further, one may shape the emissive spot to an indirectly heatedcathode. In this case the heater is shaped to run bifilarly within theemission layer support and the lead-in wires are placed exactly at thevoltage node. With extraordinary short waves it may occur that the smalldipole halves intended to collect the radiation lie at the greater partwithin the vacuum vessel or in the wall of the tube. In such case it isrecommendable to make the radiation collector equal to'an odd number ofhalf wave lengths, e. g. 3/2)\, and to arrange that one voltage nodeeach lies in the centre or the emissive spot and at the seals throughthe wall of the vessel respectively; or, alternately, one mounts thetuned dipoles, i. e. dipole designed to have a certain length, togetherwith the emission source within the vacuum. vessel.

In the Figs. 1 to 3 of the accompanying draweptember 2, 1936 ingembodiments of the invention are shown. Therein is designated by:

I the plate of a directly heated diode 9; 2 and 3 a dipole joined to theterminals of the filament 4 (2 and 3 are tuned to M2 of the decimeterwave to be received); 5 a variable resistance for adjusting the heatingcurrent supplied by the heating battery 6 and thereby at the same timethe emission of the filament 4 to the most favourable value, I anindicator, e. g. a head phone, 8 the plate battery. The filamentconsists of a tungsten-, thoriated or oxide-coated wire. Theoxide-coated filament, e. g., is made of a core of platinum or aplatinum-iridium alloy to which oxides of the alkaline earth metals, ascalcium-, strontiumor barium-oxide, together with various admixtures arepasted, fused or sintered on.

The performance of the device is as follows:-

The modulated high-frequency, which oscillates on the dipole togetherwith the inserted filament, varies the heating and thereby theemission'of the filament in time with the modulating amplitude. Theemission variations produce plate current variations in the platecircuit, which are listened to by means of head phones either directlyor through an amplifier,

To reduce still more the thermal inertia of the filament, the filament 4may be given the shape of a platinum tube about 2p. in thickness, whichis covered with oxides, if required.

Fig. 2 shows practically the same receiving device as Fig. 1. Likereference numerals represent like circuit elements. Only the cathode 10has been varied. The preferably thin-walled emissive sleeve is initiallyheated by a heater being situated within the sleeve. The wires of theheater are running in opposite directions and led out atthe centre ofthe emissive sleeve. In Fig. 3 an arrangement is shown in its principle,adapted in particular to receive very short waves. To avoid losses atthe seals of the dipole through the wall of the vessel and to be able tomake the radiation collecting part without the vessel of sufiicientlength, the whole arrangement comprising the radiation collector and thecathode, has been made equal to an odd number of half wave lengths, e.g. 3/2)., 5/2ll etc. The cathode II and the seals l2 and I3 arepositioned each at one voltage node of the stationary waves built up onthe total arrangement.

In the operation of the device of the invention, it will be appreciatedthat the extra filament heating provided by the waves collected by theantenna gives plate current in proportion to the amplitude of the extraheating current,- and hence Q.' in proportion to the amplitude of thereceived waves. This extra plate current, varying in accordance with thewave amplitude, constitutes a modulation frequency current through theheadphones.

What is claimed is:-

1. A tube detector comprising a space discharge device, radiationcollectors attached to the terminals of the cathode of said dischargedevice, an indicator coupled to the plate' circuit of said dischargedevice, the said radiation collectors together with said cathode beingso arranged that the total length amounts to 3/2x and 'one voltage nodeeach occurs at the seals through the wall of the device and at thecentre of said cathode where A is the length of the collected wave.

2. A tube detector comprising a space discharge device, radiationcollectors attached to the terminals or the cathode of saiddischargedevice, an indicator coupled to the plate circuit of said dischargedevice, the said radiation collectors together with said cathode beingso arranged that the total length is an odd multiple including unity ofhalf the length of the collected wave.

3. A tube detector comprising a space discharge device, radiationcollectors attached to the terminals of the cathode of said dischargedevice, an indicator coupled to the plate circuit of said dischargedevice, the said radiation collectors together with said cathode beingso arranged that the total length is an odd multiple including unity ofhalf the length of the collected wave, and a voltage node occurs at thecenter of said cathode.

WALTER KRIEBEL.

